Prosthetic implants such as meshes, combination mesh products or other porous prostheses are commonly used to provide a physical barrier between types of tissue or extra strength to a physical defect in soft tissue. However, such devices are often associated with post-surgical complications including post-implant infection, pain, excessive scar tissue formation and shrinkage of the prosthesis or mesh. Excessive scar tissue formation, limited patient mobility, and chronic pain are often attributed to the size, shape, and mass of the implant and a variety of efforts have been undertaken to reduce the amount of scar tissue formation. For example, lighter meshes using smaller fibers, larger weaves, and/or larger pore sizes as well as meshes woven from both non-resorbable and resorbable materials are in use to address these concerns.
For treating acute pain and infection, patients with implanted prostheses are typically treated post-operatively with systemic antibiotics and pain medications. Patients will occasionally be given systemic antibiotics prophylactically; however, literature review of clinical trials does not indicate that systemic antibiotics are effective at preventing implant-related infections.
Many types of soft tissue defects are known. For example, hernias occur when muscles and ligaments tear and allow the protrusion of fat or other tissues through the abdominal wall. Hernias usually occur because of a natural weakness in the abdominal wall or from excessive strain on the abdominal wall, such as the strain from heavy lifting, substantial weight gain, persistent coughing, or difficulty with bowel movements or urination. Eighty percent of all hernias are located near the groin but can also occur below the groin (femoral), through the navel (umbilical), and along a previous incision (incisional or ventral). Almost all hernia repair surgeries are completed with the insertion of a barrier or prosthesis to prevent their reoccurrence. Therefore products used in the management of hernias require some measure of permanent strength. The most commonly employed woven meshes are crafted from polypropylene fibers using various weaves. Tightly woven meshes with the highest strength characteristics and stiffness are very easy for the surgeon to implant; however, there appears to be a positive correlation between the tightness of the weave (correlated to surface area and stiffness), lack of patient mobility, and chronic pain. Newer meshes have larger pore structures and while they are more flexible, they are also more difficult to implant by surgeons. They are extremely difficult for laparoscopic repair, as they have very little recoil associated with them and, when rolled up to insert, they cannot be reflattened and positioned in a quick and efficient manner by the surgeon. Hence, a need still exists for surgical meshes, including hernia meshes, that have sufficient stiffness to facilitate handling and ease of insertion during surgery, yet are or can become sufficiently flexible to be comfortable after implantation.
Surgical meshes that have been manipulated to improve handling, insertion and positioning post-insertion are known in the art, but do not employ larger-pore mesh construction. For example, a laparoscopic surgical mesh with extruded monofilament PET coils or rings (e.g., the Bard® Composix® Kugel® hernia patch) increases the overall stiffness of the device and gives a shape memory to the device but does not readily allow for drug loading of the mesh, can not provide temporary stiffening of the mesh component, and can not be further shaped into a fixed three-dimensional structure after manufacture without further processing or alteration. Similarly, meshes with reinforced edges have been produced (e.g., Bard® Visilex®). These meshes have the same disadvantages as those with coils or rings. Additionally, the Kugel patch ring has been reported to break under conditions of use, causing patient morbidity and mortality.
Meshes produced from a co-weave of a biodegradable material with a non-biodegradable material have been described, e.g., the Johnson & Johnson Vypro® and Vypro II® meshes. In these meshes, polypropylene and polyglactin filaments are braided together before being knitted into a mesh. Such meshes do not change stiffness upon implant as the polyglactin fibers are very fine and flexible. The biodegradable fibers in the VyPro meshes in concert with its particular fiber weave imparts additional flexibility to the mesh such that it distends more easily than the surrounding tissue so that it is more flexible than an equivalent polypropylene fiber mesh with the same weave. Moreover, because the biodegradable polymers of that mesh may be subjected to high temperatures to produce fibers and filaments suitable for weaving, it drastically limits the drugs or biologically active agents that can be included in a biodegradable layer since, under such conditions, the vast majority of biologically-active agents and drugs are unable to withstand the manufacturing temperatures involved in fiber and filament formation. If three-dimensional structures are desired for such meshes, they must undergo further processing to attain such shapes. Finally, these meshes are often more difficult for surgeons to anchor in place because the polyglactin fiber cannot withstand the suturing tension.
The present invention overcomes these disadvantages by providing temporarily stiffened and shapeable meshes.